This invention pertains to stable carbonous catalyst particles having uniform composition of an active inorganic catalytic powder and a carbonous binder material selected for providing a basic inner porous carbon coating bonding the powder, and includes a method for making the carbonous catalyst and utilizing a catalytic process for it in catalytic reactors. Such stable carbonous catalyst particles may also include an outer porous carbon coating. These carbonous catalyst particles have adequate crush strength and attrition resistance, and can be advantageously utilized preferably in ebullated/fluidized bed catalytic reactors for various exothermic process reactions, such as catalytic conversion of synthesis gas feedstreams for producing oxygenated hydrocarbons including alcohol products.
Conventional catalyst particles having outer carbon coating for providing improved particle strength are known. For example, U.S. Pat. No. 5,037,791 to Comolli and Ganguli discloses metal oxide supported porous carbon-coated catalysts and method of making them. Such known carbon coating for porous metal-oxide catalyst particles can provide improved particle strength, reduced attrition loss and improved catalyst performance characteristics. For the Comolli et al patent, the inert support material of alumina, silica, silica-alumina, magnesia, titania and mixtures thereof provide a high surface area substrate for deposition or impregnation of active catalytic metals and their compounds, such as cobalt, chromium, iron, molybdenum, nickel, titanium, tungsten, vanadium, zinc, and combinations thereof. Such inert support materials permit preparation of small diameter (<{fraction (1/16)} inch) catalyst extrudates suitable for use in ebullated/fluidized bed reactor processes. Depending upon the composition, surface area and pore volume of these small diameter supported catalyst extrudates, they can have reasonable attrition resistance and crush strength which are improved by the outer carbon coating.
There are various other important active catalysts which consist of inorganic materials such as active metals and/or metal oxides only, and do not require or utilize high surface area support materials for deposition of the active metal components or promoters onto the support. Instead such active metal/metal oxide catalyst powders inherently have high surface area characteristics, and need not be diluted by provision of any inert high surface area support materials. However, for these active catalyst powders it is either difficult to form stable particle shapes such as extrudates, or the extrudates formed are too weak in crush strength necessary for successful use in ebullated bed or fluidized bed catalytic reactors which are desired in many commercial processes. These deficiencies for such available active catalyst powders have so far prevented commercial preparation of stable catalyst particle shapes such as small diameter extrudates having sufficient strength and attrition resistance for successful use in ebullated, fluidized or slurry bed catalytic operations. For example, cesium-promoted zinc-chromite and cesium-promoted copper-zinc-chromite are known active catalysts for converting synthesis gas feeds of CO and H2 to produce alcohol products. But because these commercial catalyst particles presently have undesirably low crush strength and low attrition resistance, fixed bed type reactors are being necessarily utilized with relatively large size catalyst particles (˜¼ inch diameter). Also, ZnO-Cr2O3 catalyst particles are used for methanol production from synthesis gas feeds, but at present only large size (˜¼ inch) catalyst particles are used in fixed bed type reactors. K-and Mn-promoted zirconia powders are also advanced catalysts useful for production of higher alcohols from synthesis gas feeds via exothermic reactions, but these catalyst powders do not allow desirable preparation of small diameter catalyst particles having sufficient crush strength and attrition resistance for successful use in ebullated bed or fluidized bed reactor operations. Because these catalytic reactions for synthesis gas feeds are highly exothermic and only limited heat transfer rates are available in such fixed bed catalytic reactors, conversion rates for the synthesis gas feed is very low and the catalyst deactivates at an undesired rapid rate. However, for such highly exothermic reactions, use of ebullated bed or fluidized bed catalytic reactors would be ideal because of their more efficient internal heat transfer resulting in achieving higher rates of synthesis gas conversion and lower rates of catalyst deactivation. Thus, having highly active smaller size strong catalyst particles such as extrudates which could be successfully utilized in ebullated, fluidized or slurry bed type reactors would be very advantageous and desirable in the chemical processing industry.
Although the stable carbonous inner carbon-coated catalyst particles of this invention can have improved particle strength, they also provide other desirable catalyst characteristics such as low acidity needed in some catalytic processes which can be successfully performed in fixed bed reactors. The basic inner carbon coating of catalyst particles allows protection of the catalyst active sites from deactivation by subsequent deposition of carbon and other catalyst poisons during process operations, because the catalysts having such inner carbon-coated acidic sites are less prone to deactivation by carbon deposition as the coating itself does not have any acidity. Also, microporous structure of the carbon coating itself can be impregnated with catalyst promoters to provide enhanced catalyst activities. These characteristics can make the stable carbonous carbon-coated catalysts suitable for any reactor configuration, including ebullated/fluidized bed and also fixed bed catalytic reactor operations where significant improvement in attrition resistance of the catalyst is not as necessary. Specifically, solid acid catalysts used for alkane isomerization are easily deactivated by carbon deposition during operations. These catalysts can be initially carbon coated to provide smooth operations with insignificant deactivation. Similarly, hydrocracking and hydrotreating catalysts can be carbon coated for smooth long term operations in fixed bed reactors. Also any difficult to form active catalyst powders can be inner carbon coated to form stable carbonous extrudates for use in fixed bed reactor operations. Also with proper carbon coating of catalysts, their attrition resistance can be increased significantly, thereby making them useful in ebullated bed, fluidized bed or slurry bed reactors which are the appropriate reactor systems for exothermic reactions.